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BQ24160A: Vsys drops out intermittently

Prodigy 190 points

Replies: 8

Views: 53

Part Number: BQ24160A

I am using the same design for the two system described here. The first system charges from the USB and runs on a battery. The second system has no battery and runs from a 5VDC supply connected to Vin.

The battery system runs OK but the other system has the intermittent drop out of Vsys. The system with the problem can run anywhere from 20 minutes to 2 weeks before the Vsys drops out. The Vsys goes from 3.6V to zero volts when it drops out. I have measured the temperature of the chip and it never goes higher than 28 degrees C.

I am showing the schematic of the circuit below. Do you have any suggestions on what might be the cause of the problem?

  • Guru 92050 points

    Hi Mike,

    The schematic pic did not show up.  For no battery operation, I recommend disabling charge and enabling no battery operation in register 1 bit 0.  What is your input current limit setting and input voltage regulation limit setting?  Is it possible that a load transient is exceeding the maximum input power per input current limit or input voltage regulation limit?

    Regards,

    Jeff

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  • In reply to Jeff F:

    Hi Jeff,

     Charging is disabled and no battery operation is set.

    The in current limit is set to 2.5A and the Vindpm is set to 4.2V.

    I don't think the load transient is exceeded because the system is in a static state and can run for 20 minutes up to about 2weeks without a failure.

     Shown below are all my register settings and the schematic.

    Register

    0      00010000

    1      00000001

    2      10001010

    3       00010110

    4       01000101

    5       00110010

    6       00000000

    7       00010000

     

  • In reply to Mike Manley:

    Hi Jeff,

     I tried a test today but I am not sure it is a valid test. To give you some information the Vsys at TP6 goes to some LDO regulators (TPS77533), so I placed a jumper from TP5 to TP6 with the switch in the off position. For the test I attached a DVM to the Vsys output, set the DVM to capture the minimum voltage, and ran the system over night. Today the DVM displayed a minimum voltage of 1.4 VDC and the present voltage of 3.6VDC. I don't know if this was a valid test because the Vsys has no load, so I don't know if this setup could cause a probelm.

  • Guru 92050 points

    In reply to Mike Manley:

    Mike,

    Regarding the registers, I don't see any issues except USB input current limit is at 100mA?  Since you are using IN, that likely is not a problem.  Regarding the schematic, I see that the TS pin resistors are the same value but you eventually intend to connect to a thermistor?  If so, one or both of those resistors will have to change.

    Can you repeat and monitor the IN pin max voltage?   This device uses forced PWM to improve transient response.  A side effect of that is the charge can momentarily run in reverse and push current back to the IN pin.  With the diode blocking current flow back to the adapter capacitors, the input capacitors may not be large enough to absorb the current, which will cause a voltage spike.  If the input voltage spikes over the charger's input voltage protection circuit (10.5V), the buck converter temporarily shuts down.  The charger has a reverse boost prevention circuit but, when you enable no battery operation, that circuit is disabled.

    Regards,

    Jeff

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  • In reply to Jeff F:

    Hi Jeff,

     What is the largest value of IN capacitor that you would recommend?

    Since the problem is very intermittent it could take two weeks  to see the problem. I will set a DVM to record the maximum voltage on the Vin pin.

    Mike

  • Guru 92050 points

    In reply to Mike Manley:

    Mike,

    Regarding the capacitor, I would try 47uF.

    Also, what is the purpose of the input diode?  The charger provides reverse blocking with its input FETs and their body diode?

    Regards,
    Jeff

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  • In reply to Jeff F:

    Hi Jeff,

    The board was designed by a consultant back in 2018, so I don't know everything about the design. I know the diodes were added to the Vin and VUSB to prevent damaging the IC if the the positive and negative power supply connections were reversed. 

    I missed the information about reverse blocking MOSFET because it is only listed on the pin functions of the data sheet. I do have a concern about reversing the 5VDC connections on Vin or VUSB because the data sheet on page 6 shows the Pin voltage range (with respect to VSS) as -2V to 20V for IN and USB.

  • Guru 92050 points

    In reply to Mike Manley:

    Mike,

    The diode is required for reverse input polarity protection.  The charger cannot protect against that.

    Regards,

    Jeff

    Please click "This resolved my issue" button if this post answers your question.